1. Field of the Invention
The present invention relates to interconnection of electrical circuits, and more particularly concerns an improved method for positioning and resiliently supporting a raised contact.
2. Description of Related Art
The ubiquitous printed circuits are being developed in ever expanding applications and continuously varying configurations. Both flexible and rigid printed circuits are connected to similar circuits and other components by means of various types of connecting devices. Test probes often have a configuration including a plurality of contacts around the perimeter of a test membrane, which contacts must electrically contact a test probe card that is mounted in a test fixture. Flat, flexible printed circuit connecting cables employ similarly configured connecting devices and have been developed to a point where connection between one such printed circuit cable and another circuit is made by providing a plurality of projecting metallic interconnection features that may be pressed against either similar features or mating metallic connecting pads on the other circuit component or components. Flexible circuit terminations or connecting wafers of this type are described in U.S. Pat. No. 4,125,310 to Patrick A. Reardon, II, deceased et al, U.S. Pat. No. 4,116,517 to Gerald J. Selvin, et al, and U.S. Pat. No. 4,453,795 to Norbert L. Moulin, et al. The connectors of these patents embody a substrate having traces chemically milled thereon with a plurality of metallic raised features later formed to project from the plane of the circuit conductors. Thus, when two such connectors are placed face to face, with the raised features in registration and contact with the other, the planes of the etched electrical circuits are suitably spaced from one another because of the projection of the features. The two circuits may be physically clamped together to press the features against one another, thereby making firm and intimate electrical contact between the two circuits.
Arrangements for manufacturing circuits with such raised contacts by electrodepositing techniques without any chemical milling are described in a co-pending application for Three-Dimensional Electroformed Circuitry of William R. Crumly, Christopher M. Schreiber and Haim Feigenbaum, filed Sep. 11, 1990, Ser. No. 07/580,758, now U.S. Pat. No. 5,197,184, which is assigned to the assignee of the present application. The disclosure of this co-pending application is incorporated herein by this reference as though fully set forth.
In the use of circuits connected by such raised contact features (sometimes called "gold dot connectors" for the gold coating of the raised features), a group of raised metallic buttons are pressed against contact pads or similar features on a facing circuit, and by virtue of their height above the plane of the circuit, separate the two facing circuits from one another. For optimum contact of all raised features of the group, all of the contacts or pads on both of the circuits must be planar, so that pressing the two circuits together will effectively cause equal contact pressure at each contact point. Because of the difficulty of maintaining precise planarity of such contact features, it has been suggested to employ contacts that are deformable, as in the Reardon U.S. Pat. No. 4,125,310, or to employ a continuous layer of resilient material, as in the U.S. Pat. No. 4,116,517 to Selvin, et al. Such arrangements are relatively complex and difficult to fabricate, and may not adequately account for actual departures from planarity of one or more of the contacts of a group. Moreover, in such arrangements the two circuits are exceedingly close to one another, being clamped together and held apart only by the height of the raised features which contact one another and effectively define the magnitude of the space between the facing circuit boards. If one or more of these raised features do not have sufficient height, it is possible that the circuit boards may contact one another. In an arrangement such as shown in the Selvin patent, where a complete sheet of elastomer is employed, the elastomer has projections precisely positioned to enter the hollow rear portion of each raised feature, and thus is exceedingly difficult to fabricate and to position during lamination of the several layers. A further problem of arrangements of the prior art is that they do not readily lend themselves to effective use in test probe circuits.
Accordingly, it is an object of the present invention to provide raised feature interconnections that avoid or minimize above mentioned problems.